1. Field of the Invention
The present invention relates to an exit monitor that examines a contamination state of a body surface of a worker due to radioactive substances when the worker working in a controlled zone of radioactive substance handling facilities exits the controlled zone.
2. Description of the Related Art
In radioactive substance handling facilities such as a nuclear plant, in order to protect workers from radiation, a controlled zone in which an access, working conditions, and the like are controlled and managed and a non-controlled zone are designated. Workers working in the controlled zone may be contaminated with radioactive substances attached thereto. Therefore, when workers exit the controlled zone to enter the non-controlled zone, the presence of contamination of workers due to radioactive substances is examined by an exit monitor. When the exit monitor has detected that a worker is contaminated with radioactive substances, the worker removes the contamination and then gets examined through the exit monitor for the presence of contamination again. When it is confirmed that the worker is free of contamination due to radioactive substances, the worker exits to the non-controlled zone.
As a related art document related to such an exit monitor, Japanese Patent Application Laid-Open No. 11-64522 entitled Exit Monitor (FIGS. 3 and 4, hereinafter JP-A 11-64522) is known, for example. The exit monitor disclosed in this related art document has a function of adjusting a height position of a radiation detector above the head of a worker particularly in accordance with the height of the worker.
The exit monitor of JP-A 11-64522 enables detection of contamination with high accuracy since it performs measurements after detecting the height of a worker and appropriately adjusting the height position of the radiation detector above the head of the worker. However, in recent years, a further improvement in detection performance is required. For example, there is an increasing demand for more reliable detection of radioactive contamination of portions (specifically, portions near the armpit between the flank and the arm, which will be described as “armpit”) where detection was considered to be difficult in the related art. However, there is no such an exit monitor at present state.
There is also a demand for simple and reliable detection of contamination due to radioactive substances including portions where detection was considered to be difficult.
Furthermore, there is a demand for an exit monitor having an inexpensive and simple structure even with an improved detection performance.
Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide an exit monitor which has an inexpensive and simple structure, and which improves both detection and cost performance by enabling detection of contamination due to radioactive substances, particularly in armpit portions between the side surfaces of a human body and the arms where detection is difficult, without being affected by the different heights of a large number of workers.